Experimental

R factor = 0.062; wR factor = 0.161; data-to-parameter ratio = 21.8. The title molecular salt, C7H9N2 +.C8H7O3 , was synthesized by reaction between benzamidine (benzenecarboximidamide) and 2-methoxybenzoic acid. In the cation, the amidinium group has two similar C—N bonds [1.3070 (17) and 1.3145 (16) Å] and is almost coplanar with the benzene ring, making a dihedral angle of 5.34 (12). In the anion, the methoxy substituent forces the carboxylate group to be twisted by 69.45 (6) with respect to the plane of the aromatic fragment. In the crystal, the components are connected by two N+—H O ()CAHB (charge-assisted hydrogen bonds), forming centrosymmetric ionic dimers with graph-set motif R2 2(8). These ionic dimers are then joined in ribbons running along the b-axis direction by another R4 2(8) motif involving the remaining N+—H O hydrogen bonds. Remarkably, at variance with the well known carboxylic dimer R2 2(8) motif, the carboxylate–amidinium pair is not planar, the dihedral angle between the planes defined by the CN2 + and CO2 atoms being 18.57 (12). Related literature For the biological and pharmacological relevance of benza-midine, see: Powers & Harper (1999). For structural analysis of proton-transfer adducts containing molecules of biologica